Field of the Invention
The present invention pertains generally to crankshafts that mechanically convert reciprocating motion to rotational motion, for example in a train, automobile, or aircraft. More specifically, in a preferred embodiment, the invention relates a carbon composite crankshaft for a piston engine made from two separate molds.
Description of the Prior Art
Heretofore, crankshafts have been known coupled to a piston cylinder arrangement via a connecting rod. Further configured to the crankshaft are journal bearings that flank the rotating connection between the rod and crankshaft. Importantly, particularly at high revolutions per minute (RPM) on the order of 3×1,000 to 5×1,000, the crankshaft will undergo complex loading to include bending and flexing as well as centrifugal stresses.
Also notable, metal crankshafts are relatively heavy and are typically made from a single body cast repeatedly forged into shape for maximum structural integrity. Since metal material such as steel has crystalline lattice structure, loads are not optimized for any particular direction. Composites, on the other hand, are vastly different wherein material layers form a lay-up. Hence, a filament can absorb structural loads only in a direction of the filament. And, lay-ups should have filaments aligned in every direction corresponding to loads which makes the fabrication process very complex.
An illustrative example of composite loading is the airplane wing. Therein, loads are received similar to an I-beam structure in that filaments on top are all in compression (toward a direction of bending stress) and the filaments on the bottom are all in tension. The filaments in the middle are all in shear. The crankshaft presents a complex problem because it's not static loaded like the airplane wing, rather instead; loads result from spinning and counter balanced rotational motion that are very dynamic. Therefore it is an object of the present invention to address multiple dynamic loading to different areas of the crankshaft. The present solution takes the top dead center bending stresses in one molding, and the spinning structural loads of the connecting rod in addition to the counter balance load in a second molding.
Further in the present global energy objective, fuel economy is paramount and market prices for petroleum based fuels are complex. Therefore, the present invention seeks to provide technologies that reduce engine load under its own weight, potentially having a profound commercial impact.
An additional parameter in crankshaft design is temperature performance. This is because components made from carbon composite begin to lose strength at a much lower 180 degrees Fahrenheit as compared to steel crankshafts which maintain performance at much higher temperatures.
In light of the above, it is an object of the present invention to provide a lightweight crankshaft wherein different parts are integrally optimized to receive differently types of loads. It is further an object of the present invention to provide an objective for laying up carbon fiber filaments in construction of a lightweight crankshaft. Still further it is an object of the present invention to provide cooling solution for a composite crankshaft.